Corporate and Tandem Structures for Combining Power from 3/sup N/ and 2N+ 1 Oscillators

The output power from three Gunn oscillators was combined using a short-slot coupler in conjunction with high-level injection locking with the power combining efficiency of ahout 100 percent at 9.7 GHz. Using the 3-oscillator structure as the building block, we constructed (3/sup 2/ = )9-oscillator corporate structure and (2X4+1=)9- and (2X6+1 = )13-oscillator tandem structures to demonstrate power combining efficiencies of 92, 95, and 93 percent, respectively, at 9.6 GHz.     

“与密钥模2~n加运算”的差分性质研究

“与密钥K模2n加”－Y=X+Kmod2ⁿ是密码算法中一个常用的基本编码环节,在SAFER++,RC6 Phelix等算法中有广泛的应用。该文对Y=X+Kmod2ⁿ进行了差分分析,首次给出了当差分转移概率取最大值1,次大值1-1/2^n-2,次小值1/2^n-2以及1/2时,输入差,输出差及密钥的结构特点和计数公式。     

Calculation of transient response

Given the rational algebraic function X(s) = an?1Sn?1+an?2Sn?2+?+a1s+a0/sn+bn?1sn?1+?+b1s+b0 it is shown that the corresponding time function is expressed simply by the linear combination x(t) = an?1qn?1(t)+an?2qn?2(t) +? +a1q1(t) + a0q0(t) where functions qt(t) are the last column elements of the transition matrix M(t) = exp (At).     

C_4H_4N_2、C_4H_2N_2和C_6N_4分子在193nm处的激光光离解——CN(X~2Σ~+)基的转动能量分布

本文描述了C_4H_4N_2、C_4H_2N_2和C_6N_4分子的紫外光离解过程。利用激光诱导荧光技术(LIF)研究了以上分子被193nm激光光解后所产生的CN(X)基的新生内能态分布。实验中观察到,CN基×~2∑~+态的0-0带和1-1带的转动分布均具有Boltzman分布的特征。CN(X)基υ″=0能级的转动温度分别为1680±40K(C_4H_4N_2)、20004±50K(C_4H_2N_2)和1470±30K(C_6N_4),而C_4H_2N_2分子所产生的CN(X)基V″=1能级的转动温度为1150±160K。本文也测量了以上三个分子在气相中的紫外吸收光谱     

Pass-Band VSWR of Maximally Flat Band-Pass Filters (Correspondence)

Microwave band-pass filters using high-Q cavity resonators can often be designed for almost negligible midband dissipation losses (i.e., <1/2 db). If these filters are designed for a maximally flat amplitude response, the insertion loss within the pass band is approximately equal to the reflection loss within the pass band. Then R = 10 log (1 + X/sup 2n/), where R = reflection loss in db X = normalized frequency variable n = number of cavity resonators.     

Ba2+掺杂对CaCu3Ti4O12陶瓷结构与电性能的影响

采用传统固相法制备了Ca1-xBaxCu3Ti4O12(x=0, 0.005, 0.010, 0.020, 0.030, 0.040, 0.050, 0100,摩尔分数) 陶瓷。用X线衍射仪、扫描电子显微镜、介电温谱测试系统及阻抗测试仪研究了Ba2+掺杂量的变化对Ca1-xBaxCu3Ti4O12陶瓷的相结构、微观形貌及电性能影响。研究结果表明,随着Ba2+掺杂量的增加,陶瓷试样产生了第二相CuO,同时Ba2+掺杂使CaCu3Ti4O12的晶格常数增大。Ca1-xBaxCu3Ti4O12陶瓷的晶粒尺寸随Ba2+掺杂量的增加而减小,气孔率随之降低。掺杂适量的Ba2+可有效降低CaCu3Ti4O12陶瓷的介电损耗,也可降低相对介电常数随温度的变化率。一定量的Ba2+掺杂还能增加CaCu3Ti4O12的晶界电阻。     

On the maximum entropy of the sum of two dependent random variables

Investigates the maximization of the differential entropy h(X+Y) of arbitrary dependent random variables X and Y under the constraints of fixed equal marginal densities for X and Y. We show that max[h(X+Y)]=h(2X), under the constraints that X and Y have the same fixed marginal density f, if and only if f is log-concave. The maximum is achieved when X=Y. If f is not log-concave, the maximum is strictly greater than h(2X). As an example, identically distributed Gaussian random variables have log-concave densities and satisfy max[h(X+Y)]=h(2X) with X=Y. More general inequalities in this direction should lead to capacity bounds for additive noise channels with feedback     

Coefficients of capture of free excitons by shallow acceptors and donors in gallium arsenide

The excitonic luminescence spectra of semi-insulating GaAs crystals with various concentrations of shallow acceptors (C) and donors (Si) were measured at 4.2 K. An analysis of these spectra made it possible to determine the coefficients of capture of free excitons by shallow neutral acceptors \([b_{A^0 X} = (4 \pm 2) \times 10^{ - 8} cm^3 /s]\)and donors \([b_{D^0 X} = (1.5 \pm 0.8) \times 10^{ - 7} cm^3 /s]\) at liquid-helium temperature and also to estimate the coefficient of capture of free excitons by shallow ionized donors \((b_{D^ + X} \gg b_{D^0 X} )\).     

A dual-mode truly modular programmable fractional divider based on a 1/1.5 divider cell

A divide-by-1/1.5 divider cell using a dual edge-trigger technique is proposed. Based on this divider cell, a dual-mode programmable divide-by-X circuit is demonstrated in 0.18-/spl mu/m CMOS technology, where X=P or P.5 in one mode and 2P or 2P+1 in the other mode with P=128-255. When operated in the divide-by-2P/2P+1 mode, this circuit outputs a signal with 50% duty cycle. Theoretically, P can be any arbitrary and programmable integer.     

A complex algorithm for linearly constrained adaptive arrays

A linearly constrained least mean squares (lms) algorithm for complex signals is derived to minimize noise power in the array output. The original algorithm for real signals isW(k + 1) = P[W(k) - mu y(k)X(k)] + F. The complex form is shown to beW(k + 1) = P[W(k) - mu y(k)bar{X}(k)] + F, where the bar abovebar{X}denotes complex conjugate.W, y, X, andFare complex.Pandmuare real.     

Asymptotic properties of delay-time-weighted probability of error (Corresp.)

Asymptotic properties of expected distortion are studied for the delay-time-weighted probability of error distortion measured_n(x,tilde{x}) = n^{-1} sum_{t=0}^{n-1} f(t + n)[l - delta(x_t,tilde{x}_t)],, wherex = (x_0,x_1,cdots,x_{n-1})andtilde{x} = (tilde{x}_0,tilde{x}_1,cdots,tilde{x}_{n-1})are source and reproducing vectors, respectively, anddelta (cdot, cdot)is the Kronecker delta. With reasonable block coding and transmission constraintsx_tis reproduced astilde{x}_twith a delay oft + ntime units. It is shown that if the channel capacity is greater than the source entropyC > H(X), then there exists a sequence of block lengthncodes such thatE[d_n(X,tilde{X})] rigjhtarrow 0asn rightarrow inftyeven iff(t) rightarrow inftyat an exponential rate. However, iff(t)grows at too fast an exponential rate, thenE[d_n(X,tilde{X})] rightarrow inftyasn rightarrow infty. Also, ifC < H(X)andf(t) rightarrow inftythenE[d_n(X,tilde{X})] rightarrow inftyasn rightarrow inftyno matter how slowlyf(t)grows.     

Spectral linewidth reduction in semiconductor lasers by an external cavity with weak optical feedback

The linewidth narrowing of a semiconductor laser due to weak optical feedback is analysed, taking into account both phase condition and threshold change for the feedback-induced modes. The achievable linewidth reduction lies in between two limiting cases, 1/(1 + X ?(1 + ?2))2 and 1/(1 + X)2, where ? and X are the linewidth enhancement factor and the feedback parameter, respectively.     

Multi-operand modulo addition using carry save adders

The authors compare two approaches for computing S= Sigma /sub i//sup k//sub =1/, X/sub i/ (mod N) using carry save adders. The biased addition technique keeps the partial carry and sum vectors C+S biased by p=2/sup n/-N where n=log/sub 2/ N. The sign estimation technique proposed computes the sign of C+S-N using a 2-bit carry look-ahead logic. The sign estimation algorithm restricts the partial sum to a smaller range, and thus, performs the final reduction faster than the biased addition algorithm.<>     

An approximation to the weight distribution of binary primitive BCH codes with designed distances 9 and 11 (Corresp.)

Recently Kasami {em et al.} presented a linear programming approach to the weight distribution of binary linear codes [2]. Their approach to compute upper and lower bounds on the weight distribution of binary primitive BCH codes of length2^{m} - 1withm geq 8and designed distance2t + 1with4 leq t leq 5is improved. From these results, the relative deviation of the number of codewords of weightjleq 2^{m-1}from the binomial distribution2^{-mt} left( stackrel{2^{m}-1}{j} right)is shown to be less than 1 percent for the following cases: (1)t = 4, j geq 2t + 1andm geq 16; (2)t = 4, j geq 2t + 3and10 leq m leq 15; (3)t=4, j geq 2t+5and8 leq m leq 9; (4)t=5,j geq 2t+ 1andm geq 20; (5)t=5, j geq 2t+ 3and12 leq m leq 19; (6)t=5, j geq 2t+ 5and10 leq m leq 11; (7)t=5, j geq 2t + 7andm=9; (8)t= 5, j geq 2t+ 9andm = 8.     

Prime-length real-valued polynomial residue division algorithms

One class of efficient algorithms for computing a discrete Fourier transform (DFT) is based on a recursive polynomial factorization of the polynomial 1-z/sup -N/. The Bruun algorithm is a typical example of such algorithms. Previously, the Bruun algorithm, which is applicable only when system lengths are powers of two in its original form, is generalized and modified to be applicable to the case when the length is other than a power of two. This generalized algorithm consists of transforms T/sub d,f/ with prime d and real f in the range 0/spl les/f<0.5. T/sub d,0/ computes residues X(z)mod(1-z/sup -2/) and X(z)mod(1-2 cos(/spl pi/k/d)z/sup -1/+z/sup -2/), k=1, 2, ..., d-1, and T/sub d,f/ (f /spl ne/0) computes residues X(z)mod(1-2cos(2/spl pi/(f+k)/d)z/sup -1/+z/sup -2/), k=0, 1, ..., d-1 for a given real signal X(z) of length 2d. The purpose of this paper is to find efficient algorithms for T/sub d,f/. First, polynomial factorization algorithms are derived for T/sub d,0/ and T/sub d,1/4/. When f is neither 0 nor 1/4, it is not feasible to derive a polynomial factorization algorithm. Two different implementations of T/sub d,f/ for such f are derived. One implementation realizes T/sub d,f/ via a d-point DFT, for which a variety of fast algorithms exist. The other implementation realizes T/sub d,f/ via T/sub d, 1/4/, for which the polynomial factorization algorithm exists. Comparisons show that for d/spl ges/5, these implementations achieve better performance than computing each output of T/sub d,f/ separately.     

Common-multiplicand multiplication and its applications to public key cryptography

Efficient computations of (X+Y/sub i/ mod i=1, 2, . . ., t; t>or=2), which is called the common-multiplicand multiplication problem, are considered. An algorithm is proposed for this problem and it is very useful for the exponentiation computations of public key cryptography.<>     

掺钪AlN材料特性及HBAR器件性能研究

该文基于掺钪AlN薄膜制备了高次谐波体声波谐振器(HBAR),研究了钪(Sc)掺杂浓度对AlN压电薄膜材料特性及器件性能的影响。研究表明,当掺入Sc的摩尔分数从0增加到25%时,压电应力系数e₃₃增加、刚度 下降,导致Al₁-_xSc_xN压电薄膜的机电耦合系数 从5.6%提升至15.8%,从而使HBAR器件的有效机电耦合系数 提升了3倍。同时,当Sc掺杂摩尔分数达25%时,Al₁-_xSc_xN(x为Sc掺杂摩尔分数)压电薄膜的声速下降13%,声学损耗提高,导致HBAR器件的谐振频率和品质因数降低。     

^39K2分子C^1Ⅱu→X^1Σg^＋跃迁的碰掸诱导光谱

用441.56nm CW He-Cd+激光获得了39K2分子C1Ⅱu→X1∑g+跃迁的碰撞诱导(CI)光谱。光谱分析表明:来自C1Ⅱu(u′=0,J′=53)的碰撞诱导跃迁是P(△J=±2)、R(△J=±2)、Q(△J=±1)。碰撞诱导谱的波数计算值和实验值之间有令人满意的符合。研究了碰撞诱导(CI)伴线和激光诱导荧光(LIF)光谱主线的强度比ρ与缓冲气体压强、样品池温度的关系,给出了物理解释。     

Mg:Er:LiNbO3晶体的激光性能和550nm寿命特性研究

本文采用Czchrzlski技术生长出优质的Mg:Er:LiNbO3[(X=2%, 4%, 6%, 8%, y=% （mol%）)]晶体,测试Mg:Er:LiNbO3晶体的光损伤阈值,红外光谱和紫外—可见吸收光谱,Mg2+浓度增加抗光损伤能力增加,其中Mg(6mol%):Er:LiNbO3和Mg(8mol%):Er:LiNbO3晶体抗光损伤阈值比LiNbO3晶体提高二个数量级以上。它们的红外光谱OH-吸收峰移到3535cm-1附近。Mg:Er:LiNbO3晶体中随着Mg2+浓度增加吸收边紫移程度增大。研究Mg:Er:LiNbO3晶体抗光损伤阈值增强机理,OH-吸收峰移动机理和吸收边移动机理。采用0.523μm激光进行泵浦获得高的利用率。在波长510—580nm范围内得到Mg:Er:LiNbO3晶体稳态发射谱。掺进4mol%的MgO是Mg:Er:LiNbO3晶体寿命最长的晶体。     

Solution of X?=A1X+XA2+D, X(0)=C and receding horizon problem

A new numerical solution for X of the general matrix differential equation X?=A1X+XA2+D, X(0)=C is considered. The new algorithm removes any restrictions on the stability requirements of A1 and A2. The proposed method provides memory as well as time saving compared to other techniques. An efficient way to solve the receding horizon control problem is established.